With all the technologically sophisticated ways of dealing with sewage, there are still millions of people without access to proper sanitation. In India, for example, 10% of cities lack a sewage system, which means most waste goes into latrines that must be cleaned by hand.

The sanitation problem in India is really a social one. "Manual scavenging" is technical illegal in India, but between 400,000 to 1.2 million people are still employed for that, depending on whom you ask.

Because most of them belong to the "untouchable" caste, manual scavengers are treated with pretty much the same aversion as the excrement they have to clean up. But in a country where raw sewage floats down the sacred Ganges River, lack of access to proper sanitation hurts everyone. Human feces is teeming with bacteria and parasites responsible for diseases such as diarrhea, cholera, and intestinal worms.